This proposal is based on the perceived need for the design and development of new biomaterials that will be utilized in repair and regeneration of tooth enamel. The major objective of our proposed study is to elucidate the molecular mechanisms involved in the formation of dental enamel with a particular emphasize on the supramolecular assembly, structure and function of the extra cellular components;amelogenin, enamelin and ameloblastin. The long-term goal is to develop biomimetic strategies for the fabrication of enamel-like materials in in vitro and in cell free systems. Our general hypothesis is that the highly organized carbonated hydroxyapatite crystals in enamel are formed through complex arrays of protein-protein and protein-mineral interactions primarily controlled by the supramolecular "chain assembly" of amelogenin nanospheres interacting with the structural motifs within enamelin and/or ameloblastin. The formation of amelogenin nanospheres and their further assembly into linear arrays are promoted by the unique secondary structure of amelogenin proteins. Specific aims: I. To investigate the nanosphere chain assembly of amelogenin in vivo and in vitro, and to elucidate secondary structure preferences within the amelogenin sequence in vitro. II. To determine the secondary structures of the 32kDa enamelin and ameloblastin fragments and to investigate their interactions with the chains of amelogenin nanosphres in vivo and in vitro. III. To investigate the interaction of amelogenin "chain assemblies" with calcium phosphate minerals in vitro, in the presence of non-amelogenins, and to develop biomimetic models for fabrication of enamel-like nanocomposites. In Summary: The principal molecular mechanisms learned from our investigation proposed in aims l-lll will contribute to our understanding of the structural biology of enamel extracellular matrix in vivo, and will provide a solid ground for the design and development of improved materials with potential application in dental and medical field. Moreover, this study will have a significant impact on the field of biomineralization, molecular self-assembly, protein structure, and understanding of pathological enamel formation.